Treatment of left laryngeal hemiplegia in standardbreds, using a nerve muscle pedicle graft.

The research investigates the effectiveness of a nerve muscle pedicle graft for treating left laryngeal hemiplegia in standardbred horses, and finds that this approach improves inspiratory impedance considerably, thereby restoring upper airway function.

Objective of Research

• The primary aim of this study is to measure the effectiveness of a nerve muscle pedicle (NMP) graft, created from the first cervical nerve and the omohyoideus muscle, in restoring the upper airway function in standardbred horses diagnosed with left laryngeal hemiplegia. This graft was transplanted into the left cricoarytenoideus dorsalis muscle of the horses under research.

Methodology

• The research involves seven adult standardbred horses that were trained to exercise on a treadmill at an inclination of 6.38 degrees.
• Both resting and exercising horses were examined at speeds of 4.2 m/s and 7.0 m/s.
• The variables analyzed included peak inspiratory and expiratory pressures in the upper airways, peak inspiratory and expiratory airflow, inspiratory and expiratory impedance, tidal volume, minute ventilation, heart rate, and respiratory frequency.
• Measurements were collected before and after left recurrent laryngeal neurectomy (LRLN), and at various time points (12, 24, and 52 weeks) post the NMP graft procedure or the sham operation.

Findings

• Prior to LRLN, exercise led to an increase in inspiratory and expiratory airflow and upper airway pressure without altering the impedance.
• Following LRLN, the airway inspiratory pressure and impedance significantly increased and inspiratory airflow drastically decreased, especially at the high exercise speed of 7.0 m/s.
• The sham operation did not improve airway function.
• Twelve weeks after the NMP graft, there were significant improvements in inspiratory impedance and airflow compared to post-LRLN measurements.
• However, 24 weeks after the NMP graft, the inspiratory impedance was not significantly different from the post-LRLN values, indicating that prolonged graft performance may be problematic.